1,2,3,4-Tetrachlorohexafluorobutane is a compound which is important as a raw material for synthesizing hexafluoro-1,3-butadiene having been noted as, for example, a fine processing etching gas for semiconductors.
As a process for producing the 1,2,3,4-tetrachlorohexafluorobutane, the following process has been hitherto known.
(1) Japanese Patent Laid-Open Publication No. 2006-342059 (patent document 1) describes a process for producing 1,2,3,4-tetrachlorohexafluorobutane by bringing a halogenated compound represented by CClX1X2—CClX3—CClX4—CClX5X6 (X is a hydrogen atom or a fluorine atom) into contact with fluorine gas in a liquid phase.
In this process, a reaction solvent is used. The patent document 1 describes that perfluoroalkanes, perfluoroethers, perfluoropolyethers, chlorinated fluorinated hydrocarbons and perfluoroalkylamines are used as the reaction solvents.
However, if a reaction solvent is used as above, it is necessary to separate the reaction product from the reaction solvent. Although the separated reaction solvent can be separated from the product, recovered and recycled, it cannot be denied that the operation of separating the reaction solvent is complicated. When 1,2,3,4-tetrachlorohexafluorobutane is used as a reaction solvent, there is an advantage that the separation between the reaction solvent and the product is unnecessary. In this reaction, however, the fluorination reaction is carried out with a low concentration of the reaction raw material diluted with a reaction solvent, so that from the viewpoint of industrially efficient production of a desired product, a problem is left.
As described above, in the conventional process, the reaction solvent is used as an essential component and therefore, there is also a problem that the operation of separating it is extremely complicated.
Patent document 1: Japanese Patent Laid-Open Publication No. 2006-342059